Improvement sn steam-boilers



J. 'MILLHOLLAND.

Steam Boiler Fire Tube.

No. 8,742. I Patented Feb. I7, 1852.

NITED STATES ATENT rrrcE,

JAMES MILLHOLLAND, OF READING, PENNSYLVANIA.

IMPROVEMENT EN STEAM-BOILERS.

Specification forming part of Letters Patent No. @,74%, dated February17, 1852-.

To all whom it may concern: Be it known that I, JAMES l\IILLHOLLAND, 0Reading, in the county of Berks and State of Pennsylvania, have inventedcertain new and useful Improvements in Steam-Boilers and Furnacestherefor, with a view to adapt them the better to the use of coal asfuel, which improvements are particularly applicable tolocomotive-engines for railroads; and I do hereby declare that thefollowing is a full, clear, and exact description of my saidimprovement, reference being had to the accompanying drawings, whichform part of this specification, and in which- Figure 1 represents avertical longitudinal section through the middle of a locomotiveboiler.Fig. 2 is a plan of the fire-box, and

-Figr3-is'a transverse section through the supplementarycombustion-chamber.

It has long been a desideratum to obtain a locomotive-engine with itsfurnace and boiler constructed in such manner that anthracite coal couldbe employed successfully as the fuel for generating steam, because ofits cheapness and great heating-power; but the intensity of the heatgenerated by this fuel when supplied with a sufficient quantity of airto insure its thorough combustion has generally acted with suchenergetic and destructive effect upon the sides of the fire-box as torender its use exceedingly difficult and its economy doubtful.

The object of my invention is to protect the fire-box from overheatingand at the same time to insure the most thorough and complete combustionof the coal burned therein. The means I have adopted to attain this endis to place a contracted grate in the fire-box, which by excluding theair from direct access to the outer margin. of the coal keeps down theheat sufficiently to protect the sides of the box; but in doing this alarge volume of inflammable gas is allowed to pass off unburned, andtherefore without producing the proper heating effect or generating thequantity of steam due to the consumption of fuel, which defect, if notremedied, would preclude the use of the contracted grate, as it woulddiminish the efficiency of the engine, to maintain which is the firstconsideration in point of importance; but I have provided for thecompletion of the combustion of the gases thus evolved from the coal bycombining with thecontracted grate a supplementary chamber of combustionwhich is duly supplied with air and arranged in a well-known mannerbetween the fire-box and the smokebox and connected with both by flues.Those which communicate with the fire-box, for more efficiency, shouldbe of large area to conduct the gases freely into the chamber where theyare to be burned, and those which communicate with the smoke-box ofsmall area, that they may not allow the burning gases and flame toescape too freely, and also that they maypresent a largeevaporatingsurface to absorb the heat more readily from the escapinggases.

In the accompanying drawings, A is the firebox; B, the steam-dome; C,the smoke-box; D, the cylindrical shell which connects the firebox andsmoke-box and contains the supplementary chamber of combustion, E, thesmall tubular flues F, which connect the chamber with the smoke-box, andthe larger tubular fines, G, which connect the chamber with the firebox.The lines G are considerably larger than those ordinarily used inlocomotiveboilers to give an enlarged area for the passage of theunburned gases from the fire-box into the combustion-chamber.

The fiues F are of the size ordinarily used in locomotives and are morenumerous than the fines G, so that with a large evaporatingsurface theiraggregate areais sufficiently contracted to prevent the escape of theburning gases and flame without giving time to absorb their heat.

To complete the combustion of the inflammable gases in the intermediatechamber, E, atmospheric air is injected into the chamber from anair-box, II, which is introduced into the lower part of the chamber. Thetop of this box is perforated with numerous small holes, through whichthe air passes into the chamber in a corresponding number of small jets.A pipe, j, supplies the chamber with air, which in this instance iscaused to pass through the ash-pit and there get warmed by the wasteheat on its way to the pipe.

The grate occupies the usual position in the fire-box A; but its area iscontracted by mar= ginal plates K, or otherwise, to a sufficient extentto afford a lodgment for a stratum of ashes all around the lower part ofthe sides of the fire-box to protect them from the intense heat of theburning coals. These plates also prevent the air from passing upimmediately at the sides of the boX and thussuffer the coals around themargin of the fire adjagent to the sides of the box to burn with lessheat and evolve a large volume of inflammable gas, which passes offthrough the flues G into the chamber E to be mixed with air and burned.

The draft in this boiler may be generated in the usual manner by asteam-blast in the chimney, as well to draw air through the grate intothe fire-box as to draw it through the pipe j and wind-chest H into thesupplementary chamber of combustion.

The slackening of the current of gas and flame while passing through thesupplementary combustion-chamber causes a precipitation into the bottomof the chamber of the greater portion of the ashes carried by the draftfrom the fire-box. The ashes thus precipitated must from time to time bewithdrawn bya door arranged for the purpose in the bottom of thechamber. The enlarged flues G, by giving free vent to the hot gases,lower the temperature of the fire-box and thereby prolong its duration,which is further increased by the contraction of the grate, whichprevents the direct contact of the draft with the sides of the box andpermits the accumulation of a lining of ashes around the lower edge ofthe side plates. -With these advantages is also combined a considerablesaving of fuel; but the chief merit and advantage of this arrangement isits distribution of the burning of the fuel and of the heat evolvedthereby through two chambers of combustion, which prevents the excessiveand destructive concentration of heat which occurs when the combustionof anthracite coal is completed in a single chamber of theneoessarily-contracted dimensions of the fire-box of a locomotive.

Having thus described myimprovements in locomoti ve-boilers,what Iclaim'therein asnew, and desire to secure by Letters Patent, is-

The contracted grate in the fire-box, in combination with asupplementary chamber of combustion supplied with air and situated at apoint intermediate between the fire-box and smoke-box which is connectedwith the former and the latter by fines, in the manner substantially asherein described.

In testimony whereof I have hereunto subscribed my name.

JAMES MILLHOLLAND.

Witnesses:

D. A. GRIFFITH, J. O. ALLEN.

